Certain methods are available for cell processing, including large-scale methods and methods for use in preparation of cells for adoptive cell therapy. For example, methods for viral vector transfer, e.g., transduction, selection, isolation, stimulation, culture, washing, and formulation, are available. Available methods have not been entirely satisfactory. Improved methods are needed, for example, for large-scale processing, e.g., transduction, of cells for adoptive cell therapy. For example, methods are needed to improve efficiency and reproducibility, and to reduce time, cost, handling, complexity, and/or other parameters associated with such production. Among the provided embodiments are methods, systems, and kits addressing such needs.